The present invention relates to golf balls including a controlled-isomer polybutadiene in the core, as well as methods for forming the same. In particular, the controlled-isomer polybutadiene is a low modulus composition.
Multi-layer golf balls contain a core, which may include one or more layers of solid material or one or more layers of solid material encompassing a fluid therein, and a cover. Optionally, an elastic winding may also be used to form a layer surrounding the center to provide certain playing characteristics. Such balls are known as xe2x80x9cwoundxe2x80x9d balls. The multi-layer golf balls discussed herein include a core and a cover. The terms xe2x80x9ccorexe2x80x9d or xe2x80x9cball core,xe2x80x9d as used herein, include a center having one or more layers and a mantle formed of one or more layers. The terms xe2x80x9ccenterxe2x80x9d or xe2x80x9cball center,xe2x80x9d as used herein, include a solid and/or fluid mass around which a mantle and a cover are disposed. The mantle is disposed between the center and the cover, typically in concentric fashion, with the cover being the outermost portion of the ball.
A variety of golf ball compositions are known and used in various methods of manufacture. Compositions typically including greater than 35 percent cis-1,4-polybutadiene isomer and preferably greater than 90 percent cis-polybutadiene isomer are often used in forming golf ball cores, or a portion thereof. A number of references disclosing various cis-polybutadiene materials are discussed below.
U.S. Pat. No. 3,239,228 discloses a solid golf ball having a core molded of polybutadiene rubber with a high sulfur content, and a cover. The polybutadiene content of the core is stereo-controlled to the configuration 25-100 percent cis- and 0-65 percent trans-1,4-polybutadiene, with any remainder having a vinyl configuration of polybutadiene. A preferred embodiment of the polybutadiene golf ball core contains 35 percent cis-, 52 percent trans-, and 13 percent vinyl-polybutadiene. The level of trans- and vinyl-content are disclosed to be unimportant to the overall playing characteristics of the polymer blend.
U.S. Pat. No. 3,666,272 discloses solid golf balls and compositions used therein including polybutadiene elastomer having at least 35 percent cis-content, gum plastic, inert inorganic filler, polyfunctional co-curing monomer ester, and a free-radical initiator.
British Patent No. 1,168,609 discloses a molding composition from which improved golf ball cores can be molded and which contains cis-polybutadiene as a basic polymer component. The core polymer component typically includes at least 60 percent cis-polybutadiene, with the remainder being either the trans- or vinyl-forms of polybutadiene. In a preferred embodiment, the core polybutadiene component contains 90 percent cis-configuration, with the remaining 10 percent being either the trans- or vinyl-configurations of 1,4-polybutadiene.
British Patent No. 1,209,032 discloses a two- or three-piece golf ball having a core and a cover. The core or cover material can be any material capable of being crosslinked. In particular, the material can be a polymer or a copolymer of butadiene or isoprene. Preferably, the polymer component is polybutadiene having a cis content of greater than 50 percent by weight.
U.S. Pat. Nos. 3,572,721 and 3,572,722 disclose a solid, one- or two-piece golf ball, with the two-piece ball having a core and a cover. The cover material can include any one of a number of materials, or blends thereof, known to those of ordinary skill in the art, including trans-polybutadiene which may be present in an amount from at least 90 percent, with the remainder being the cis- and/or vinyl configuration.
U.S. Pat. Nos. 3,896,102; 3,926,933; 4,020,007; and 4,020,008 disclose a 1,3-butadiene component and a method and catalyst for preparing trans-polybutadiene, and that it is well known that increasing content of trans-polybutadiene is more resinous and produces a more elastic, tough, crystalline, thermoplastic solid. The ""933 and ""008 patents further disclose that trans-polybutadiene is resistant to attack by ozone and other chemical agents, and is typically used in insulation, battery cases, and golf ball covers.
U.S. Pat. No. 3,992,014 discloses a one-piece, solid golf ball. The golf ball material is typically polybutadiene, with a stereo-configuration selected to be at least 60 percent cis-polybutadiene, with the remaining 40 percent being the trans-polybutadiene and/or 1,2-polybutadiene (vinyl) isomers.
U.S. Pat. No. 4,020,115 discloses the preparation of homopolymers and random copolymers of butadiene with styrene and/or isoprene that include butadiene units having a low vinyl content of not over 12 percent and a trans-polybutadiene structure of from about 70 to 81 percent. These polymers are disclosed to have broad molecular weight distribution, as well as tack and green-strength desired for manufacturing tires. A variety of trans-polybutadiene and vinyl-polybutadiene materials are also disclosed with the catalysts used for the preparation thereof.
U.S. Pat. No. 4,683,257 discloses solid golf balls formed from a blend of polybutadienes prepared with nickel and/or cobalt base catalysts and a lanthanide rare earth element base catalyst, each containing at least 40 percent cis-polybutadiene isomer.
U.S. Pat. No. 4,919,434 discloses a two-piece golf ball having a solid core of more than 40% cis-1,4-polybutadiene isomer and a cover having an inner layer of 0.1 to 2 mm thickness and an outer layer of 0.1 to 1.5 mm thickness. The inner layer is a thermoplastic resin, such as an ionomer, polyester elastomer, polyamide elastomer, thermoplastic urethane elastomer, propylene-butadiene copolymer, 1,2-polybutadiene, polybutene-1, and styrene-butadiene block copolymer, either individually or in combination.
U.S. Pat. No. 4,929,678 discloses a rubber composition for golf balls including at least 40 percent by weight polybutadiene rubber with a Mooney viscosity of 45 to 90 and a cis-bond content of at least 80 percent, a co-crosslinking agent, and a peroxide. These polymers are disclosed to have a dispersity of between 4.0 to 8.0, which is a ratio of weight average molecular weight to number average molecular weight.
U.S. Pat. No. 4,931,376 discloses butadiene polymers and copolymers with another conjugated diene having at least 80 percent butadiene by weight; 60 to 98 percent trans-polybutadiene linkages; a molecular weight distribution of 1.1 to 4.0; melting temperature of 40xc2x0 C. to 130xc2x0 C.; and a content of insolubles in boiling cyclohexane of 1% or less, as well as processes for making the same. Weight average molecular weights of 30,000 to 300,000 and trans-polybutadiene contents greater than about 30 percent are preferred. These materials are disclosed for use in golf ball covers, splint or gyps material, and the like.
U.S. Pat. No. 4,955,613 discloses golf balls made from two polybutadienes, each having a Mooney viscosity below about 50 and a cis-polybutadiene isomer content of greater than about 40 percent, more preferably greater than about 90 percent, and catalysts for preparing the polybutadienes.
U.S. Pat. No. 4,971,329 discloses solid golf balls made from polybutadiene mixtures of about 99.5 to 95 weight percent cis-1,4-polybutadiene and about 0.5 to 5 weight percent vinyl-1,2-polybutadiene. The cis-polybutadiene is made by blending from about 80 percent to 100 percent by weight of cis-polybutadiene with a cis-content of 95 percent and about 0 weight percent to 20 weight percent of cis-polybutadiene with a cis-content of about 98 percent.
U.S. Pat. No. 5,141,233 discloses rubber compositions and golf balls made therewith, where the compositions include at least one natural and/or synthetic rubber component, fine inorganic fibers subjected to surface treatment with an agent and a non-sulfur type vulcanizing agent to provide excellent durability, bounce impact elasticity, and excellent feeling on hitting. The compositions should include at least 30 percent cis-polybutadiene isomer content.
U.S. Pat. No. 5,252,652 discloses a one-piece or multi-layered golf ball core with improved flying performance from a rubber composition comprising a base rubber, preferably 1,4-polybutadiene with a cis-content of at least 40 mole percent, an unsaturated carboxylic acid metal salt, an organic peroxide, and an organic sulfur compound and/or a metal salt thereof. The organic sulfur compound and/or a metal salt is typically present in an amount from about 0.05 to 2 parts per hundred by weight and the organic peroxide is typically present in an amount from about 0.5 to 3 parts per hundred by weight of the total polymer component.
European Patent No. 0 577 058 discloses a golf ball containing a core and a cover that is formed as two separate layers. The inner layer of the cover is molded over the core and is formed from ionomer resin. The outer layer of the cover is molded over the inner layer and is formed from a blend of natural or synthetic balata and a crosslinkable elastomer, such as polybutadiene. In one embodiment of the outer layer of the cover, the elastomer is 1,4-polybutadiene having a cis-structure of at least 40 percent, with the remaining 60 percent being the trans-isomer. A preferred embodiment contains a cis-structure of at least 90 percent and more preferably, a cis-structure of at least 95 percent.
U.S. Pat. No. 5,697,856 discloses a solid golf ball having a core and a cover wherein the core is produced by vulcanizing a base rubber composition containing a butadiene rubber having a cis-polybutadiene structure content of not less than 90 percent before vulcanization. The amount of trans-polybutadiene structure present after vulcanization is 10 to 30 percent, as amounts over 30 percent are alleged to detrimentally result in cores that are too soft with deteriorated resilience performance, and to cause a decrease in golf ball performance. The core includes a vulcanizing agent, a filler, an organic peroxide, and an organosulfur compound.
British Patent No. 2,321,021 discloses a solid golf ball having a core and a cover formed on the core and having a two-layered cover construction having an inner cover layer and an outer cover layer. The outer cover layer is comprised of a rubber composite that contains 0.05 to 5 parts by weight of an organic sulfide compound. The core rubber composition comprises a base rubber, preferably 1,4-polybutadiene having a cis-content of at least 40 percent by weight, a crosslinking agent, a co-crosslinking agent, an organic sulfide, and a filler.
U.S. Pat. No. 5,833,553 discloses core compositions including polybutadiene, natural rubber, metallocene catalyzed polyolefins, polyurethanes, and other thermoplastic or thermoset elastomers, and mixtures thereof having a broad molecular weight range of 50,000 to 500,000, preferably from 100,000 to 500,000. Polybutadiene with a high cis-content is noted as being preferred.
U.S. Pat. No. 5,861,465 discloses thread rubber for wound golf balls having rubber component obtained by vulcanizing rubber composition including rubber selected from natural rubber, synthetic high-cis-polyisoprene rubber, and mixtures with at least one specific diaryl disulfide, a vulcanizing agent, and an antioxidant.
U.S. Pat. No. 6,018,007 discloses the preparation of trans-polybutadiene and other polymers and copolymers having trans configuration in the conjugated diene monomer contributed units with improved catalyst systems. The resulting polymers are rubbery, except those with high trans content, and may be vulcanized by well known methods and incorporated in tires, general rubber goods, and plastics materials.
Additionally, conventional polymers that have a high percentage of the trans-polybutadiene conformation, such as DIENE 35NF, which has 40 percent cis-isomer and 50 percent trans-polybutadiene isomer and which is available commercially from Firestone Corp. DIENE 35NF, however, does not by itself provide for the high resilience values and low modulus desired in golf balls and therefore is not believed to be desirable for such applications.
Polybutadiene polymers used in the prior art tend to exhibit low resilience at low crosslink density. Golf ball manufacturers generally increase the golf ball resilience by increasing the concentration of crosslinking agents. Unfortunately, although increased crosslinks leads to a high coefficient of restitution, they also result in undesirably high modulus materials. High modulus materials provide high compression balls with undesirable feel when struck with a golf club.
It is thus desired to prepare single- and multi-layer golf balls containing low modulus compositions. It is alternatively desired to obtain the same or lower modulus while achieving greater resilience.
The invention relates to two-piece golf balls having a core and a cover disposed over the core, as well as other multi-layered golf balls having a core including a center and at least one intermediate layer disposed over the center, and at least one cover layer disposed over the core. The controlled-isomer polybutadiene of the present invention may be used in any portion of the golf ball core, although in one preferred embodiment it is included in the center. It should also be understood that the golf ball may include one or more wound layers in the core, each such layer having at least one tensioned elastomeric thread wound about the center or another intermediate layer. The controlled-isomer polybutadiene of the invention may also be used to form the one or more threads for such a wound layer, either alone or in combination with controlled-isomer polybutadiene being used in other portions of the core. The invention also relates to a multi-layer ball having a fluid center surrounded by a shell to contain the fluid, wherein at least one intermediate layer about such a fluid-filled center includes the controlled-isomer polybutadiene.
The invention relates to a golf ball having a core including a material formed from a controlled-isomer polybutadiene polymer, a crosslinking agent, and a free-radical initiator, or a reaction product thereof; and a cover having a plurality of dimples disposed about the core, wherein the controlled-isomer polybutadiene includes at least about 10 percent to 80 percent trans-isomer and no more than about 9 percent vinyl-isomer. In one embodiment, the controlled-isomer polybutadiene has both an absolute molecular weight of at least about 210,000 and a polydispersity of no more than about 3 prior to crosslinking. In one embodiment, the controlled isomer polybutadiene includes from about 20 percent to 60 percent trans-isomer. In a preferred embodiment, the controlled isomer polybutadiene includes from about 15 percent to 80 percent trans-isomer.
In various embodiments, the isomers may be randomly, pseudo-randomly, or block distributed, although the random or pseudo-random distributions are preferred. In one embodiment, the cover has at least one of a dimple coverage of greater than about 60 percent, a hardness from about 35 to 80 Shore D, or a flexural modulus of greater than about 500 psi, and wherein the golf ball has at least one of a compression from about 50 to 120 or a coefficient of restitution of greater than about 0.7.
In a preferred embodiment, the core has an effective modulus of no greater than about 10,000 psi. In a more preferred embodiment, the core has an effective modulus of no greater than about 8,000 psi. In one embodiment, the controlled-isomer polybutadiene has less than about 5 percent vinyl-polybutadiene, while in another embodiment the amount is less than about 3 percent vinyl-polybutadiene. In another embodiment, the controlled-isomer polybutadiene has an absolute molecular weight average of at least about 210,000, while in another embodiment the controlled-isomer polybutadiene has both an absolute molecular weight of at least about 300,000. In a preferred embodiment, the controlled-isomer polybutadiene has an absolute molecular weight average of at least about 350,000. In another embodiment, the controlled-isomer polybutadiene has a polydispersity of no greater than about 2.5. In a preferred embodiment, the controlled-isomer polybutadiene has a polydispersity of no greater than about 2. In one embodiment, the controlled-isomer polybutadiene is provided in the form of regrind having a particle size of about 0.1 micrometers to 1000 micrometers. In one embodiment, the controlled-isomer polybutadiene has a substantially uniform amount of trans-isomer after polymerization.
In one embodiment, the core includes a center and at least one intermediate layer. In one embodiment, the controlled-isomer polybutadiene material is disposed in the center. In another embodiment, either alternatively or in addition to the above embodiment, at least one of the intermediate layers includes the controlled-isomer polybutadiene. In another embodiment, the center includes a fluid. In yet another embodiment, at least one of the intermediate layers includes a tensioned elastomeric thread wound about the center. In this situation, the tensioned elastomeric thread includes the controlled-isomer polybutadiene in one embodiment.
The invention also relates to a method of preparing a golf ball, which includes combining a crosslinking agent, a free-radical initiator, and an uncrosslinked controlled-isomer polybutadiene having an absolute molecular weight of at least about 210,000 and a polydispersity of no more than about 3 to form a core mixture; forming a golf ball core having a material comprising the core mixture, or a product thereof; and providing a cover having a plurality of dimples about the core, wherein the controlled-isomer polybutadiene includes at least about 10 percent to 80 percent trans-isomer and no more than about 9 percent vinyl-isomer.
The core forming step can include the steps of forming a center and providing at least one intermediate layer about the center. In one embodiment, the center includes the controlled-isomer polybutadiene. In another embodiment, the at least one intermediate layer comprises the controlled-isomer polybutadiene and the center comprises a fluid.